Are we playing this grand slam Down Under or just upside-down? The pattern of surprise results continued on Wednesday when defending champion Victoria Azarenka emulated her opposite number Novak Djokovic by going out at the quarter-final stage.

This was the fifth singles match on the trot, across both men’s and women’s draws, that had finished in victory for the lower-ranked player. After the heatwave that buckled Melbourne’s tram tracks during the first week of this Australian Open, the second week has delivered enough shockwaves to bring down the local power lines.

Just as Djokovic’s conqueror, Stan Wawrinka, came into Tuesday night with a terrible record against the defending champion, so Agnieszka Radwanska – Aga to her friends – was not expected to trouble Azarenka overmuch. She had lost their last seven meetings, overpowered on each occasion by the weight of the Belarussian’s groundstrokes.

But Radwanska possesses great touch, even if she lacks the physical strength of her rivals, and she was able to keep Azarenka off balance with her drop shots and delicate volleys.

The deciding set went by in a flash as she claimed a 6-1, 5-7, 6-0 victory, making this the first Australian Open where both defending champions had fallen in the quarter-finals.

Asked about her anticipation and guile, Radwanska replied: “It’s something that you practise for so many years. Of course, maybe I was born with that, not serving 200 per hour but mixing up everything, running a lot.”

The Aga saga was due to continue overnight when she faced the 5ft 3in Dominika Cibulkova – one of the few women in the top 100 who is shorter than her – in a semi-final that few would have predicted at the start of the fortnight.

Cibulkova has produced a giantkilling act of her own this week, putting out Maria Sharapova in the fourth round, and on Wednesday she followed up by defeating Romania’s Simona Halep 6-3, 6-0 in a one-sided quarter-final.

“I just couldn’t play today,” said Halep, who had never reached the last eight of a grand slam before. “I had emotions, big emotions, and I couldn’t manage this. Before the match I was very nervous and I didn’t feel the ball at all. I couldn’t move my body and I couldn’t play.”

At 22, Halep is perhaps best known for undergoing breast reduction surgery five years ago to improve her mobility. Yet if she continues to climb the rankings – she already stands at No 11, and can expect to crack the top 10 after her run in Melbourne – she will soon get used to playing in the second week of slams.